No problem for that, it's a critique after all, so harshness is expected.

gentle stress -> was experimenting with a neon glow effect that seemed fine when the background is black. I C&Ped that to there and it turned out like that.

Jack and Mark Get Busy! -> whoops, the noise effect is too strong, eh? Maybe I'll tone it down a little. It looked somewhat fine to me, though.

Monkey Dance -> both text has the same effects, maybe because the I stretched it too big? Anyway, if I centered the monkey's head, there will be some empty space on the left, so this was intended to leave no extra space behind.

super highway -> lol, that's Posterizer's fault. The photo was too real, thus I want to lower the realism by applying that filter, so that's not really artifacts. You can say it's intended

*All the songs that are not included (feeling of love, The Least 100sec, Turning the motor over, IMPLANTATION, quick master, fffff, Kodomo no Rakugaki Chou & Tamayura) are (or were) already on pop'n music, except fffff which IS from pop'n music 13)